Custom JavaScript prototype class for generating dates

custom-date.js

var wk = wk || {};

$(document).ready(function () {
    var _monthNames = [
        'January',
        'February',
        'March',
        'April',
        'May',
        'June',
        'July',
        'August',
        'September',
        'October',
        'November',
        'December'
    ];

    /**
     * Set to public since this method is accessed in a few places
     * @param {number} month Month in digit format form 0 - 11
     * @return {string}
     */
    wk.dateGetMonthName = function (month) {
        return _monthNames[month];
    };

    /**
     * Constructor for a date
     * @param {string} date Date processed by Date.new()
     * @returns {self}
     */
    wk.Date = function (date) {
        this.setDate(date);
        return this;
    };

    /**
     * Uses a UTC date
     * @url http://stackoverflow.com/questions/439630/how-do-you-create-a-javascript-date-object-with-a-set-timezone-without-using-a-s
     * @param date
     * @returns {*}
     */
    wk.Date.prototype.setDate = function (date) {
        this.timestamp = new Date(date);
        return this;
    };

    wk.Date.prototype.getTimestamp = function () {
        return this.timestamp;
    };

    wk.Date.prototype.getUTCTimestamp = function () {
        return this.timestamp.toUTCString();
    };

    wk.Date.prototype.getTimestampTomorrow = function () {
        return new Date(this.timestamp.getTime() + (24 * 60 * 60 * 1000));
    };

    wk.Date.prototype.getMonthName = function () {
        return _monthNames[this.timestamp.getUTCMonth()];
    };

    wk.Date.prototype.getFriendly = function () {
        return this.timestamp.getUTCFullYear() + '-' + ('0' + (this.timestamp.getUTCMonth() + 1)).slice(-2) + '-' + ('0' + this.timestamp.getUTCDate()).slice(-2);
    };

    wk.Date.prototype.getFancy = function () {
        var month = _monthNames[this.timestamp.getUTCMonth()].substr(0, 3),
            day = this.timestamp.getUTCDate(),
            year = this.timestamp.getUTCFullYear();

        return month + ' ' + day + ', ' + year;
    };

    wk.Date.prototype.subtractDays = function (days) {
        this.timestamp.setDate(this.timestamp.getUTCDate() - days);
        return this.timestamp;
    };
});